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Abstract:

An electrode assembly includes a cell stack part having (a) a structure
in which one kind of radical unit is repeatedly disposed, or (b) a
structure in which at least two kinds of radical units are disposed in a
predetermined order. The one kind of radical unit has a four-layered
structure in which first electrode, first separator, second electrode and
second separator are sequentially stacked or a repeating structure in
which the four-layered structure is repeatedly stacked. Each of the at
least two kinds of radical units are stacked by ones to form the
four-layered structure or the repeating structure. The separator has a
larger size than the electrode to expose an edge part of the separator to
outside of the electrode and the separator. The edge parts of the
separators included in one radical unit or in the cell stack part are
attached to form a sealing part.

Claims:

1. An electrode assembly, comprising: a cell stack part having (a) a
structure in which one kind of radical unit is repeatedly disposed, the
one kind of radical unit having same number of electrodes and separators
which are alternately disposed and integrally combined, or (b) a
structure in which at least two kinds of radical units are disposed in a
predetermined order, the at least two kinds of radical units each having
same number of electrodes and separators which are alternately disposed
and integrally combined; wherein the one kind of radical unit of (a) has
a four-layered structure in which a first electrode, a first separator, a
second electrode and a second separator are sequentially stacked together
or a repeating structure in which the four-layered structure is
repeatedly stacked; wherein each of the at least two kinds of radical
units of (b) are stacked by ones in the predetermined order to form the
four-layered structure or the repeating structure in which the
four-layered structure is repeatedly stacked, wherein the separator has a
larger size than the electrode to expose an edge part of the separator to
the outside of the electrode and the separator; and wherein the edge
parts of the separators included in one radical unit are attached to each
other to form a sealing part, or the edge parts of the separators
included in the cell stack part are attached to each other to form the
sealing part.

2. The electrode assembly of claim 1, further comprising a separator
additionally stacked on an uppermost or lowermost electrode of the cell
stack part.

3. The electrode assembly of claim 1, wherein the sealing part is formed
by placing the edge parts of adjacent separators to meet each other and
by applying heat and pressure.

4. The electrode assembly of claim 3, wherein an applying time of the
heat and the pressure to the edge parts of the adjacent separators to
form the sealing part is 3 to 5 seconds.

5. The electrode assembly of claim 3, wherein the pressure applied to the
edge parts of the adjacent separators to form the sealing part is smaller
than a pressure applied to attach the electrode to the separator in each
of the radical units.

6. The electrode assembly of claim 1, wherein the radical unit is not
bonded to the adjacent radical unit in the cell stack part, or is bonded
to the adjacent radical unit in the cell stack part by means of a bonding
strength differing from a bonding strength between the electrode and the
separator in the radical unit.

7. The electrode assembly of claim 1, wherein the one kind of radical
unit of (a) comprises a first radical unit having the four-layered
structure or the repeating structure in which the four-layered structure
is repeatedly stacked, and wherein the cell stack part has a structure in
which the first radical units are repeatedly disposed.

8. The electrode assembly of claim 1, wherein the at least two kinds of
radical units of (b) comprises: a second radical unit having the first
electrode, the first separator, the second electrode, the second
separator, the first electrode, and the first separator, which are
sequentially disposed and integrally combined; and a third radical unit
having the second electrode, the second separator, the first electrode,
the first separator, the second electrode, and the second separator,
which are sequentially disposed and integrally combined, and wherein the
cell stack part has a structure in which the second radical unit and the
third radical unit are alternately disposed.

9. The electrode assembly of claim 1, wherein the one kind of radical
unit is provided in plurality and the plurality of one kind of radical
units is classified into at least two groups having different sizes, and
wherein the cell stack part has a structure in which a plurality of steps
is formed by stacking the one kind of radical units of (a) according to
the size thereof.

10. The electrode assembly of claim 1, wherein the one kind of radical
unit of (a) is provided in plurality and the plurality of the one kind of
radical units is classified into at least two groups having different
geometric shapes, and wherein the cell stack part has a structure in
which a plurality of steps is formed by stacking the one kind of radical
units of (a) according to the geometric shape thereof.

11. The electrode assembly of claim 1, wherein the electrode is attached
to an adjacent separator in each radical unit.

12. The electrode assembly of claim 11, wherein an entire surface of the
electrode facing the adjacent separator is attached to the adjacent
separator.

13. The electrode assembly of claim 11, wherein the attachment between
the electrode and the separator is provided by applying pressure to the
electrode and the adjacent separator or by applying pressure and heat to
the electrode and the adjacent separator.

14. The electrode assembly of claim 11, wherein adhesive strength between
the electrode and the adjacent separator in the radical unit is greater
than adhesive strength between the radical units in the cell stack part.

15. The electrode assembly of claim 11, wherein the separator comprises a
porous separator base material and a porous coating layer that is applied
to an entire surface of one side or both sides of the separator base
material, wherein the porous coating layer comprises a mixture of
inorganic particles and a binder polymer, wherein the binder polymer
binds and fixes the inorganic particles to each other, and wherein the
electrode is attached to the adjacent separator by the coating layer.

16. The electrode assembly of claim 15, wherein the inorganic particles
of the porous coating layer have a densely packed structure to form
interstitial volumes between the inorganic particles over the overall
coating layer, and wherein a pore structure is formed in the coating
layer by the interstitial volumes that are defined by the inorganic
particles.

17. The electrode assembly of claim 1, wherein the cell stack part
further comprises a first auxiliary unit stacked on a terminal electrode
that is an uppermost or a lowermost electrode, wherein, when the terminal
electrode is a cathode, the first auxiliary unit is formed by stacking
from the terminal electrode, a separator, an anode, a separator, and a
cathode in sequence, and wherein, when the terminal electrode is an
anode, the first auxiliary unit is formed by stacking from the terminal
electrode, a separator and a cathode in sequence.

18. The electrode assembly of claim 17, wherein the cathode of the first
auxiliary unit comprises: a current collector; and an active material
coated on only one side facing the radical unit among both sides of the
current collector.

19. The electrode assembly of claim 1, wherein the cell stack part
further comprises a second auxiliary unit on a terminal separator that is
an uppermost or a lowermost separator, wherein, when the electrode
contacting the terminal separator is a cathode in the radical unit, the
second auxiliary unit is formed by stacking from the terminal separator,
an anode, a separator and a cathode in sequence, and wherein, when the
electrode contacting the terminal separator is an anode in the radical
unit, the second auxiliary unit is formed as a cathode.

20. The electrode assembly of claim 19, wherein the cathode of the second
auxiliary unit comprises: a current collector; and an active material
coated on only one side facing the radical unit among both sides of the
current collector.

21. The electrode assembly of claim 1, wherein the cell stack part
further comprises a first auxiliary unit stacked on a terminal electrode
disposed on an uppermost or a lowermost electrode, wherein, when the
terminal electrode is a cathode, the first auxiliary unit is formed by
stacking from the terminal electrode, a separator and an anode in
sequence, and wherein, when the terminal electrode is an anode, the first
auxiliary unit is formed by stacking from the terminal electrode, a
separator, a cathode, a separator and an anode in sequence.

22. The electrode assembly of claim 21, wherein the first auxiliary unit
further comprises a separator at an outer side of the anode.

23. The electrode assembly of claim 1, wherein the cell stack part
further comprises a second auxiliary unit on a terminal separator that is
an uppermost or a lowermost separator, wherein, when the electrode
contacting the terminal separator is a cathode in the radical unit, the
second auxiliary unit is formed as an anode, and wherein, when the
electrode contacting the terminal separator is an anode in the radical
unit, the second auxiliary unit is formed by stacking from the terminal
separator, a cathode, a separator, and an anode in sequence.

24. The electrode assembly of claim 23, wherein the second auxiliary unit
further comprises a separator at an outer side of the anode.

25. The electrode assembly of claim 1, wherein the cell stack part
further comprises a second auxiliary unit stacked on a terminal separator
that is an uppermost or a lowermost separator, and wherein, when the
electrode contacting the terminal separator in the radical unit is an
anode, the second auxiliary unit is formed by stacking from the terminal
separator, a first cathode, a separator, an anode, a separator, and a
second anode in sequence.

26. The electrode assembly of claim 25, wherein the second cathode of the
second auxiliary unit comprises: a current collector; and an active
material coated on only one side facing the radical unit among both sides
of the current collector.

27. The electrode assembly of claim 1, wherein the cell stack part
further comprises a second auxiliary unit stacked on a terminal separator
that is an uppermost or a lowermost separator, and wherein, when the
electrode contacting the terminal separator is a cathode in the radical
unit, the second auxiliary unit is formed by stacking from the terminal
separator, a first anode, a separator, a cathode, a separator, and a
second anode in sequence.

28. A method of manufacturing an electrode assembly, the method
comprising: a step of forming one kind of a radical unit having an
alternately stacked structure of a same number of electrodes and
separators, or at least two kinds of radical units having an alternately
stacked structure of a same number of electrodes and separators (S10); a
step of forming a sealing part by facing edge parts of the separators
included in one radical unit and applying heat and pressure (S20); and a
step of forming a cell stack part by repeatedly stacking the one kind of
the radical units after performing Steps S10 and S20, or by stacking the
at least two kinds of the radical units after performing Steps S10 and
S20 in a predetermined order (S22); wherein the one kind of radical unit
has a four-layered structure in which a first electrode, a first
separator, a second electrode and a second separator are sequentially
stacked together or a repeating structure in which the four-layered
structure is repeatedly stacked; and wherein each of the at least two
kinds of radical units are stacked by ones in the predetermined order to
form the four-layered structure or the repeating structure in which the
four-layered structure is repeatedly stacked.

29. A method of manufacturing an electrode assembly, the method
comprising: a step of forming one kind of a radical unit having an
alternately stacked structure of a same number of electrodes and
separators, or at least two kinds of radical units having an alternately
stacked structure of a same number of electrodes and separators (S10); a
step of forming a cell stack part by repeatedly stacking the one kind of
the radical units, or by stacking the at least two kinds of the radical
units in a predetermined order (S14); and a step of forming a sealing
part by facing edge parts of the separators included in the cell stack
part and applying heat and pressure (S30); wherein the one kind of
radical unit has a four-layered structure in which a first electrode, a
first separator, a second electrode and a second separator are
sequentially stacked together or a repeating structure in which the
four-layered structure is repeatedly stacked; and wherein each of the at
least two kinds of radical units are stacked by ones in the predetermined
order to form the four-layered structure or the repeating structure in
which the four-layered structure is repeatedly stacked.

30. The method of manufacturing an electrode assembly of claim 28,
wherein Step S20 is performed by applying the heat of 50.degree. C. to
100.degree. C. and the pressure of 10 gf/cm2 to 20 gf/cm2 to
the edge parts of the separators.

31. The method of manufacturing an electrode assembly of claim 28,
wherein an applying time of the heat and the pressure to the edge parts
of the adjacent separators to form the sealing part is 3 to 5 seconds.

32. The method of manufacturing an electrode assembly of claim 28,
wherein the pressure applied to the edge parts of the adjacent separators
is smaller than a pressure applied to attach the electrode to the
separator.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the priority of Korean Patent Application
Nos. 10-2013-0114246 filed on Sep. 26, 2013, in the Korean Intellectual
Property Office, the disclosures of which are incorporated herein by
reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an electrode assembly with
improved stability and a method of manufacturing the same, and more
particularly, to an electrode assembly with improved stability capable of
decreasing shrinkage ratio of a separator and a method of manufacturing
the same.

[0004] 2. Description of the Related Art

[0005] Secondary batteries receive attention as a power source of an
electric vehicle (EV), a hybrid electric vehicle (HEV), a parallel hybrid
electric vehicle (PHEV), etc., suggested as a means for solving the air
pollution of a common gasoline vehicle, a diesel vehicle, etc. using
fossil fuel. In a medium and large size device such as a vehicle, high
power and high capacity are necessary, and a medium and large size
battery module in which a plurality of battery cells are electrically
connected is used.

[0006] However, since the medium and large size battery module is
preferably manufactured to have a small size and light weight, a
prismatic type battery, a pouch type battery, etc. having high stacking
degree and light weight with respect to capacity have been mainly
manufactured as the battery cell of the medium and large size battery
module.

[0007] In general, an electrode assembly is classified according to the
structure of the electrode assembly having a cathode/separator/anode
structure, and typically is classified into a jelly-roll type (roll type)
electrode assembly having a rolled structure of long sheet type cathodes
and anodes with a long sheet type separator disposed therebetween, and a
stack-type (laminated type) electrode assembly obtained by stacking a
plurality of cathodes and anodes cut into a certain size with a separator
therebetween in sequence. Preferably, the structure of the electrode
assembly includes a stack-type structure and a stack/folding type
structure.

[0008] The stack type structure is widely known in the art, and the
explanation thereon will be omitted in the present disclosure. Detailed
description of an electrode assembly having the stack/folding type
structure is disclosed in Korean Patent Application Publication Nos.
2001-0082058, 2001-0082059 and 2001-0082060 filed by the present
Applicant.

[0009] Referring to FIG. 1, in an electrode assembly of a stack/folding
type structure 1, a plurality of radical units 1a, 1b, 2, 3 and 4,
including a cathode, a separator and an anode stacked in sequence are
overlapped, and in each of overlapped parts, a separator sheet 5 is
interposed. The separator sheet 5 has a length for wrapping the radical
units and is disposed at the overlapped parts of the radical units while
wrapping each of the radical units from the radical unit 1a to the
outermost radical unit 4 continuously.

[0010] The terminal part of the separator sheet 5 is finished by heat
welding, by attaching using an adhesive tape 6, or the like. The
stack/folding type electrode assembly is manufactured by arranging the
radical units 1a, 1b, 2, 3 and 4 on the separator sheet 5 having a long
length and rolling the separator sheet 5 from one terminal part thereof
one by one. However, in this structure, temperature gradient may be
generated between the radical units 1a, 1b and 2 positioned in the center
portion and the radical units 3 and 4 positioned at the outer portion,
thereby generating different heat emitting efficiencies. Thus, lifetime
may decrease after use for a long time.

[0011] In general, a separator provided in a radical unit is mainly formed
by using a polymer material, and has shrinking properties by heat. An
overcharge test and a hot box test are performed with respect to an
electrode assembly or a secondary battery including the same to evaluate
stability. During performing the tests, some bad electrode assemblies or
secondary batteries including the same may ignite. The ignition may be
generated because of the shrinkage of the separator due to heat and the
short generated through the contact of a cathode and an anode.

[0012] Meanwhile, even in a commercial secondary battery after performing
the test for stability evaluation, a risk of the shrinkage of a separator
due to heat applied from the outside during use or heat generated in the
secondary battery, and the generation of short as described above is
present.

[0013] To prevent the above defects, a separator having a larger size than
an electrode may be applied in an electrode assembly.

[0014] However, in the electrode assembly of a stack/folding type
structure 1, the edge parts of a separator are not attached to an
electrode, and a series of manufacturing processes of a secondary battery
is conducted without conducting specific treatment with respect to the
edge parts of the separator. Thus, there is a high risk of generating
short due to overcharge, overheat, etc. In addition, since specific
treatment with respect to the edge parts of the separator is not
conducted in an electrode assembly of a stack type structure, there also
is a high risk of generating short as in the electrode assembly of a
stack/folding type structure 1.

[0015] Thus, both in the electrode assembly of a stack/folding type
structure 1 and the electrode assembly of the stack type, the separator
is necessary to have a quite large size when compared to the electrodes
to definitely prevent the generation of short between the cathode and the
anode. In this case, the volume of the secondary battery may increase.

[0016] Here, since the separator is more than necessary, the production
cost of a secondary battery may increase.

SUMMARY OF THE INVENTION

[0017] An aspect of the present disclosure for solving the above-described
defects provides an electrode assembly having decreased risk of inner
short and improved stability even though using a separator having the
same as or a somewhat smaller size of that of a common separator, and a
method of manufacturing the same.

[0018] Another aspect of the present invention is to provide an electrode
assembly having decreased unit production cost and having improved
stability, and a manufacturing method thereof.

[0019] A further aspect of the present invention is to provide an
electrode assembly with improved stability and a manufacturing method
thereof by which the electrode assembly may be manufactured only using
one kind of bi-cells.

[0020] According to an aspect of the present disclosure, there is provided
an electrode assembly with improved stability including a cell stack part
having (a) a structure in which one kind of radical unit is repeatedly
disposed, the one kind of radical unit having a same number of electrodes
and separators which are alternately disposed and integrally combined, or
(b) a structure in which at least two kinds of radical units are disposed
in a predetermined order, the two kinds of radical units having a same
number of electrodes and separators which are alternately disposed and
integrally combined. The one kind of radical unit of (a) has a
four-layered structure in which a first electrode, a first separator, a
second electrode and a second separator are sequentially stacked together
or a repeating structure in which the four-layered structure is
repeatedly stacked, and each of the at least two kinds of radical units
of (b) are stacked by ones in the predetermined order to form the
four-layered structure or the repeating structure in which the
four-layered structure is repeatedly stacked. The separator has a larger
size than the electrode to expose an edge part of the separator to the
outside of the electrode and the separator. The edge parts of the
separators included in one radical unit are attached to each other to
form a sealing part, or the edge parts of the separators included in the
cell stack part are attached to each other to form the sealing part.

[0021] According to another aspect of the present disclosure, there is
provided a method of manufacturing an electrode assembly with improved
stability including a step of forming one kind of a radical unit having
an alternately stacked structure of a same number of electrodes and
separators, or at least two kinds of radical units having an alternately
stacked structure of a same number of electrodes and separators (S10); a
step of forming a sealing part by facing edge parts of the separators
included in one radical unit and applying heat and pressure (S20); and a
step of forming a cell stack part by repeatedly stacking the one kind of
the radical units after performing steps S10 and S20, or by stacking the
at least two kinds of the radical units after performing steps S10 and
S20 in a predetermined order (S22). The one kind of radical unit has a
four-layered structure in which a first electrode, a first separator, a
second electrode and a second separator are sequentially stacked together
or a repeating structure in which the four-layered structure is
repeatedly stacked, and each of the at least two kinds of radical units
are stacked by ones in the predetermined order to form the four-layered
structure or the repeating structure in which the four-layered structure
is repeatedly stacked.

[0022] According to further another aspect of the present disclosure,
there is provided a method of manufacturing an electrode assembly with
improved stability including a step of forming one kind of a radical unit
having an alternately stacked structure of a same number of electrodes
and separators, or at least two kinds of radical units having an
alternately stacked structure of a same number of electrodes and
separators (S10); a step of forming a cell stack part by repeatedly
stacking the one kind of the radical units, or by stacking the at least
two kinds of the radical units in a predetermined order (S14); and a step
of forming a sealing part by facing edge parts of the separators included
in the cell stack part and applying heat and pressure (S30). The one kind
of radical unit has a four-layered structure in which a first electrode,
a first separator, a second electrode and a second separator are
sequentially stacked together or a repeating structure in which the
four-layered structure is repeatedly stacked, and each of the at least
two kinds of radical units are stacked by ones in the predetermined order
to form the four-layered structure or the repeating structure in which
the four-layered structure is repeatedly stacked.

[0023] According to the present invention, the following effects may be
obtained.

[0024] First, an electrode assembly having decreased risk of inner short
and improved stability even though using a separator having the same as
or a somewhat smaller size of that of a common separator, and a method of
manufacturing the same, may be provided.

[0025] Second, an electrode assembly having decreased production cost and
having improved stability and a method of manufacturing the same, may be
provided.

[0026] Third, an electrode assembly having improved stability and a method
of manufacturing the same by which the electrode assembly may be
manufactured only using one kind of bi-cells, may be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and other aspects, features and other advantages of the
present invention will be more clearly understood from the following
detailed description taken in conjunction with the accompanying drawings,
in which:

[0028] FIG. 1 is a cross-sectional view conceptually illustrating a
folding type structure of a common electrode assembly;

[0029] FIG. 2 is a side view illustrating a first structure of a radical
unit according to the present disclosure;

[0030] FIG. 3 is a side view illustrating a second structure of a radical
unit according to the present disclosure;

[0031] FIG. 4 is a side view illustrating a cell stack part formed by
stacking the radical units of FIG. 2;

[0032] FIG. 5 is a side view illustrating a third structure of a radical
unit according to the present disclosure;

[0033] FIG. 6 is a side view illustrating a fourth structure of a radical
unit according to the present disclosure;

[0034] FIG. 7 is a side view illustrating a cell stack part formed by
stacking the radical units of FIG. 5 and the radical units of FIG. 6;

[0035] FIG. 8 is a process diagram illustrating a manufacturing process of
a radical unit according to the present disclosure;

[0036] FIG. 9 is a perspective view illustrating a cell stack part formed
by stacking radical units having different sizes;

[0037] FIG. 10 is a side view illustrating the cell stack part of FIG. 9;

[0038] FIG. 11 is a perspective view illustrating a cell stack part formed
by stacking radical units having different geometric shapes;

[0039] FIG. 12 is a side view illustrating a first structure of a cell
stack part including a radical unit and a first auxiliary unit according
to the present disclosure;

[0040] FIG. 13 is a side view illustrating a second structure of a cell
stack part including a radical unit and a first auxiliary unit according
to the present disclosure;

[0041] FIG. 14 is a side view illustrating a third structure of a cell
stack part including a radical unit and a second auxiliary unit according
to the present disclosure;

[0042] FIG. 15 is a side view illustrating a fourth structure of a cell
stack part including a radical unit and a second auxiliary unit according
to the present disclosure;

[0043] FIG. 16 is a side view illustrating a fifth structure of a cell
stack part including a radical unit and a first auxiliary unit according
to the present disclosure;

[0044] FIG. 17 is a side view illustrating a sixth structure of a cell
stack part including a radical unit and a first auxiliary unit according
to the present disclosure;

[0045] FIG. 18 is a side view illustrating a seventh structure of a cell
stack part including a radical unit and a second auxiliary unit according
to the present disclosure;

[0046] FIG. 19 is a side view illustrating an eighth structure of a cell
stack part including a radical unit and a second auxiliary unit according
to the present disclosure;

[0047] FIG. 20 is a side view illustrating a ninth structure of a cell
stack part including a radical unit and a first auxiliary unit according
to the present disclosure;

[0048] FIG. 21 is a side view illustrating a tenth structure of a cell
stack part including a radical unit, a first auxiliary unit, and a second
auxiliary unit according to the present disclosure;

[0049] FIG. 22 is a side view illustrating an eleventh structure of a cell
stack part including a radical unit and a second auxiliary unit according
to the present disclosure;

[0050] FIG. 23 is a cross-sectional view illustrating a stacked state of a
separator on the first structure of the radical unit in FIG. 2;

[0051] FIG. 24 is a cross-sectional view illustrating a stacked state of a
separator on an uppermost electrode after stacking the first structure of
the radical unit in FIG. 2 twice;

[0052] FIG. 25 is a cross-sectional view illustrating a cell stack part
including a sealing part by attaching edge parts of the separators in
FIG. 23; and

[0053] FIG. 26 is a cross-sectional view illustrating a cell stack part
including a sealing part by attaching edge parts of the separators in
FIG. 23.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0054] Exemplary embodiments of an electrode assembly with improved
stability and a method of manufacturing the same according to the present
disclosure will now be described in detail with reference to the
accompanying drawings.

[0055] It will be understood that terms, such as those defined in commonly
used dictionaries, should be interpreted as having a meaning that is
consistent with their meaning in the context of the relevant art and will
not be interpreted in an idealized or overly formal sense unless
expressly so defined herein. Rather, these embodiments are provided so
that this disclosure will be thorough and complete, and will fully convey
the scope of the inventive concept to those skilled in the art. Although
the preferred embodiments of the present disclosure have been disclosed
for illustrative purpose, those skilled in the art will appreciate that
various modifications, additions and substitutions can be made without
departing from the scope and spirit of the inventive concept as defined
in the accompanying claims.

[0056] In the drawings, the sizes and relative sizes of each elements or a
specific part composing the elements may be exaggerated or briefly
illustrated for effective explanation and clearance of technical
contents. Thus a real size is not reflected to the size of each element.
Particular explanation on relevant known functions or constituents is
considered to unnecessarily confuse the gist of the present disclosure,
the explanation will be omitted.

[0057] An electrode assembly according to the present disclosure includes
a cell stack part having a structure obtained by stacking radical units
repeatedly or in a predetermined order, or having a structure obtained by
further stacking an auxiliary unit on the cell stack part. In addition, a
sealing part may be formed by attaching the edge parts of separators
having a larger size than electrodes by the radical unit, or a sealing
part may be formed by attaching the edge parts of all separators present
in the cell stack part having a structure obtained by stacking radical
units repeatedly or in a predetermined order at the same time.

[0058] The structure of the radical unit and the auxiliary unit possibly
stacked on the radical unit, and the structure of the cell stack part
having a plurality of stacked radical units may be attained diversely.
Therefore, these structures will be explained first, and the formation of
the sealing part in the radical unit or the formation of the sealing part
in the cell stack part at the same time will be subsequently explained.

Cell Stack Part

[0059] The cell stack part has a structure obtained by repeatedly
disposing one kind of radical units or a structure obtained by disposing
at least two kinds of radical units in a predetermined order, for
example, alternately. This will be described below in more detail.

[Structure of Radical Unit]

[0060] In an electrode assembly according to the present disclosure, a
radical unit is formed by alternately disposing electrodes and
separators. Here, the same number of electrodes and separators are
disposed. For example, as illustrated in FIG. 2 a radical unit 110a may
be formed by stacking two electrodes 111 and 113 and two separators 112
and 114. Here, a cathode and an anode may naturally face each other
through the separator. When the radical unit is formed as described
above, an electrode 111 is positioned at one end part of the radical unit
(see electrode 111 in FIGS. 2 and 2) and a separator 114 is positioned at
the other end part of the radical unit (see separator 114 in FIGS. 2 and
2).

[0061] The electrode assembly according to the present disclosure is
basically characterized in that the cell stack part or electrode assembly
is formed by only stacking the radical units. That is, the present
disclosure has a basic characteristic in that the cell stack part is
formed by repeatedly stacking one kind of radical unit or by stacking at
least two kinds of radical units in a predetermined order. To realize the
above-described characteristic, the radical unit may have the following
structure.

[0062] First, the radical unit may be formed by stacking a first
electrode, a first separator, a second electrode, and a second separator
in sequence. In more detail, a first electrode 111, a first separator
112, a second electrode 113, and a second separator 114 may be stacked in
sequence from an upper side to a lower side, as illustrated in FIG. 2, or
from the lower side to the upper side, as illustrated in FIG. 3, to form
radical units 110a and 110b. The radical unit having the above-described
structure may be referred to as a first radical unit. Here, the first
electrode 111 and the second electrode 113 may be opposite types of
electrodes. For example, when the first electrode 111 is a cathode, the
second electrode 113 may be an anode.

[0063] As described above, when the radical unit is formed by stacking the
first electrode 111, the first separator 112, the second electrode 113,
and the second separator 114 in sequence, a cell stack part 100a may be
formed by only repeatedly stacking the one kind of radical units 110a, as
illustrated in FIG. 4. Here, the radical unit may have an eight-layered
structure or twelve-layered structure in addition to a four-layered
structure. That is, the radical unit may have a repeating structure in
which the four-layered structure is repeatedly disposed. For example, the
radical unit may be formed by stacking the first electrode 111, the first
separator 112, the second electrode 113, the second separator 114, the
first electrode 111, the first separator 112, the second electrode 113,
and the second separator 114 in sequence.

[0064] Alternatively, the radical unit may be formed by stacking the first
electrode 111, the first separator 112, the second electrode 113, the
second separator 114, the first electrode 111, and the first separator
112 in sequence, or by stacking the second electrode 113, the second
separator 114, the first electrode 111, the first separator 112, the
second electrode 113, and the second separator 114 in sequence. The
radical unit having the former structure may be referred to as a second
radical unit and the radical unit having the latter structure may be
referred to as a third radical unit.

[0065] In more detail, the second radical unit 100c may be formed by
stacking the first electrode 111, the first separator 112, the second
electrode 113, the second separator 114, the first electrode 111, and the
first separator 112 in sequence from the upper side to the lower side, as
illustrated in FIG. 5. Also, the third radical structure 110d may be
formed by stacking the second electrode 113, the second separator 114,
the first electrode 111, the first separator 112, the second electrode
113, and the second separator 114 in sequence from the upper side to the
lower side, as illustrated in FIG. 6. As noted above, the stacking may be
conducted in sequence from the lower side to the upper side.

[0066] When only one of the second radical units 110c and one of the third
radical units 110d are stacked, a repeating structure in which the
four-layered structure is repeatedly stacked may be formed. Thus, when
the second radical unit 110c and the third radical unit 110d are
alternately stacked one by one, the cell stack part 100b may be formed by
stacking only the second and third radical units, as illustrated in FIG.
7. For reference, when three kinds of radical units are prepared, the
cell stack part may be formed by stacking the radical units in a
predetermined order, for example, the first radical unit, the second
radical unit, the third radical unit, the first radical unit again, the
second radical unit, and the third radical unit.

[0067] As described above, the one kind of radical unit in the present
disclosure has a four-layered structure in which a first electrode, a
first separator, a second electrode and a second separator are
sequentially stacked, or has a repeating structure in which the
four-layered structure is repeatedly stacked. Also, at least two kinds of
radical units in the present disclosure are stacked only by ones in a
predetermined order to form the four-layered structure or the repeating
structure in which the four-layered structure is repeatedly disposed. For
example, the first radical unit forms a four-layered structure by itself,
and the second radical unit and the third radical unit form a
twelve-layered structure by stacking one of each, that is, two radical
units in total.

[0068] Thus, the cell stack part or electrode assembly may be formed only
by stacking, that is, by repeatedly stacking one kind of radical unit or
by stacking at least two kinds of radical units in a predetermined order.

[0069] The cell stack part of the present disclosure may be formed by
stacking the radical units one by one. That is, the cell stack part may
be manufactured by forming the radical units and then stacking the
radical units repeatedly or in a predetermined order. As described above,
the cell stack part of the present disclosure may be formed by only
stacking the radical units. Therefore, the radical units of the present
disclosure may be very accurately aligned. When the radical unit is
accurately aligned, the electrode and the separator may also be
accurately aligned in the cell stack part. In addition, the cell stack
part or electrode assembly may be improved in productivity. This is done
because the manufacturing process is very simple.

[Manufacture of Radical Unit]

[0070] A manufacturing process of the first radical unit will be
exemplarily described with reference to FIG. 8. First, a first electrode
material 121, a first separator material 122, a second electrode material
123 and a second separator material 124 are prepared. Here, the first
separator material 122 and the second separator material 124 may be the
same. The first electrode material 121 is cut into a certain size through
a cutter C1, and the second electrode material 123 is cut into a certain
size through a cutter C2. Then, the first electrode material 121 is
stacked on the first separator material 122, and the second electrode
material 123 is stacked on the second separator material 124.

[0071] Then, it is preferable that the electrode materials and the
separator materials are attached to each other through laminators L1 and
L2. Through the attachment, a radical unit in which the electrodes and
the separators are integrally combined may be formed. The combining
method may be diverse. The laminators L1 and L2 may apply pressure to the
materials or apply pressure and heat to the materials to attach the
materials to each other. Because of the attachment, the stacking of the
radical units may be more easily performed while manufacturing the cell
stack part. Also, the alignment of the radical units may be also easily
accomplished because of the attachment. After the attachment, the first
separator material 122 and the second separator material 124 are cut into
a certain size through a cutter C3 to manufacture the radical unit 110a.

[0072] As described above, the electrode may be attached to the adjacent
separator in the radical unit. Alternatively, the separator may be
attached to the adjacent electrode. Here, it is preferable that an entire
surface of the electrode facing the adjacent separator is attached to the
adjacent separator. In this case, the electrode may be stably fixed to
the separator. Typically, the electrode has a size less than that of the
separator.

[0073] For this, an adhesive may be applied to the separator. However,
when the adhesive is used, it is necessary to apply the adhesive over an
adhesion surface of the separator in a mesh or dot shape. This is because
if the adhesive is closely applied to the entire adhesion surface,
reactive ions such as lithium ions may not pass through the separator.
Thus, when the adhesive is used, it is difficult to allow the overall
surface of the electrode to closely attach to the adjacent separator.

[0074] Alternatively, use of the separator including the coating layer
having adhesive strength makes it possible to generally attach the
electrode to the separator. This will be described below in more detail.
The separator may include a porous separator base material such as a
polyolefin-based separator base material and a porous coating layer that
is generally applied to one side or both sides of the separator base
material. Here, the coating layer may be formed of a mixture of inorganic
particles and a binder polymer that binds and fixes the inorganic
particles to each other.

[0075] Here, the inorganic particles may improve thermal stability of the
separator. That is, the inorganic particles may prevent the separator
from being contracted at a high temperature. In addition, the binder
polymer may fix the inorganic particles to improve mechanical stability
of the separator. Also, the binder polymer may attach the electrode to
the separator. Since the binder polymer is generally distributed in the
coating layer, the electrode may closely adhere to the entire adhesion
surface of the separator, unlike the foregoing adhesive. Thus, when the
separator is used as described above, the electrode may be more stably
fixed to the separator. To enhance the adhesion, the above-described
laminators may be used.

[0076] The inorganic particles may have a densely packed structure to form
interstitial volumes between the inorganic particles over the overall
coating layer. Here, a pore structure may be formed in the coating layer
by the interstitial volumes that are defined by the inorganic particles.
Due to the pore structure, even though the coating layer is formed on the
separator, the lithium ions may smoothly pass through the separator. For
reference, the interstitial volume defined by the inorganic particles may
be blocked by the binder polymer according to a position thereof.

[0077] Here, the densely packed structure may be explained as a structure
in which gravels are contained in a glass bottle. Thus, when the
inorganic particles form the densely packed structure, the interstitial
volumes between the inorganic particles are not locally formed in the
coating layer, but generally formed in the coating layer. As a result,
when each of the inorganic particles increases in size, the pore formed
by the interstitial volume also increases in size. Due the
above-described densely packed structure, the lithium ions may smoothly
pass through the separator over the entire surface of the separator.

[0078] The radical units may also adhere to each other in the cell stack
part. For example, if the adhesive or the above-described coating layer
is applied to a bottom surface of the second separator 114 in FIG. 2, the
other radical unit may adhere to the bottom surface of the second
separator 114.

[0079] Here, the adhesive strength between the electrode and the separator
in the radical unit may be greater than that between the radical units in
the cell stack part. It is understood, that the adhesive strength between
the radical units may not be provided. In this case, when the electrode
assembly or the cell stack part is disassembled, the electrode assembly
may be separated into the radical units due to a difference in the
adhesive strength. For reference, the adhesive strength may be expressed
as delamination strength. For example, the adhesive strength between the
electrode and the separator may be expressed as a force required for
separating the electrode from the separator. In this manner, the radical
unit may not be bonded to the adjacent radical unit in the cell stack
part, or may be bonded to the adjacent radical unit in the cell stack
part by means of a bonding strength differing from a bonding strength
between the electrode and the separator.

[0080] For reference, when the separator includes the above-described
coating layer, it is not preferable to perform ultrasonic welding on the
separator. Typically, the separator has a size greater than that of the
electrode. Thus, there may be an attempt to bond the edge of the first
separator 112 to the edge of the second separator 114 through the
ultrasonic welding. Here, it is necessary to directly press an object to
be welded through a horn in the ultrasonic welding. However, when the
edge of the separator is directly pressed through the horn, the separator
may adhere to the horn due to the coating layer having the adhesive
strength. As a result, the welding apparatus may be broken down.

[Modification of Radical Unit]

[0081] Until now, the radical units having the same size have been
explained. However, the radical units may have different sizes. When
stacking the radical units having different sizes, cell stack parts
having various shapes may be manufactured. Herein, the size of the
radical unit is explained with reference to the size of the separator,
because, typically, the separator is larger than the electrode.

[0082] Referring to FIGS. 9 and 10, a plurality of radical units is
prepared and may be classified into at least two groups having different
sizes (see reference numerals 1101a, 1102a and 1103a in FIG. 10). By
stacking the radical units according to their sizes, a cell stack part
100c having a structure of a plurality of steps may be formed. FIGS. 9
and 10 illustrate an embodiment in which the cell stack part includes
three steps obtained by stacking the radical units 1101a, 1102a and 1103a
classified into three groups, in which the radical units having the same
size are stacked together, is illustrated. For reference, the radical
units included in one group may form two or more steps.

[0083] When the plurality of steps is formed as described above, it is
preferable that the radical unit has a structure of the first radical
unit, that is, the above-described four-layered structure or the
repeating structure in which the four-layered structure is repeatedly
stacked. (Herein, the radical units are considered to be included in one
kind of radical unit even though the radical units have the same stacked
structures but have different sizes.)

[0084] Preferably, the same number of cathodes and the anodes are stacked
in one step. Also, it is preferable that opposite electrodes face each
other through a separator between one step and another step. For example,
in case of the second and third radical units, two kinds of the radical
units are necessary for forming one step.

[0085] However, in case of the first radical unit, only one kind of
radical unit is necessary for forming one step as illustrated in FIG. 10.
Thus, when the radical unit has the four-layered structure or the
repeating structure in which the four-layered structure is repeatedly
stacked, number of kinds of radical units may decrease even though a
plurality of the steps is formed.

[0086] Also, in case of the second and the third radical units, at least
one of the two kinds of the radical units are necessary to be stacked to
form one step. Thus, the one step may have at least a twelve-layered
structure. However, in case of the first radical unit, only one kind of
radical unit is necessary to be stacked to form one step. Thus, one step
may have at least a four-layered structure. As a result, when the radical
unit has the four-layered structure or the repeating structure in which
the four-layered structure is repeatedly stacked, the thickness of each
step may be easily controlled when forming a plurality of steps.

[0087] The radical units may have not only different sizes but also
different geometric shapes. For example, the radical units may have
different sizes and different edge shapes, and may or may not have a
through hole as illustrated in FIG. 11. More particularly, as illustrated
in FIG. 11, a plurality of radical units classified into three groups may
form three steps by stacking the radical units having the same geometric
shapes. For this, the radical units may be classified into at least two
groups (each of the groups has different geometric shape). Similarly, the
radical unit may preferably have the four-layered structure or the
repeating structure in which the four-layered structures are repeatedly
stacked, that is, the structure of the first radical unit. (Herein, the
radical units are considered to be included in one kind of radical unit
even though the radical units have the same stacked structure but have
different geometric shapes.)

[Auxiliary Unit]

[0088] The cell stack part may further include at least one among a first
auxiliary unit and a second auxiliary unit. First, the first auxiliary
unit will be described below. In the present disclosure, an electrode is
positioned at one end of the radical unit, and a separator is positioned
at the other end of the radical unit. When the radical units are stacked
in sequence, the electrode may be positioned at the uppermost portion or
at the lowermost portion of the cell stack part (see reference numeral
116 in FIG. 12, and this electrode may be referred to as a terminal
electrode 116). The first auxiliary unit is additionally stacked on the
terminal electrode.

[0089] In more detail, when the terminal electrode 116 is a cathode, the
first auxiliary unit 130a may be formed by stacking outward from the
terminal electrode 116, a separator 114, an anode 113, a separator 112,
and a cathode 111 in sequence, as illustrated in FIG. 12. On the other
hand, when the terminal electrode 116 is an anode, the first auxiliary
unit 130b may be formed by stacking outward from the terminal electrode
116, the separator 114, and the cathode 113 in sequence, as illustrated
in FIG. 13.

[0090] In the cell stack parts 100d and 100e, a cathode may be positioned
at the outermost portion of a terminal electrode through the first
auxiliary units 130a and 130b, as illustrated in FIGS. 12 and 13. In this
case, in the cathode positioned at the outermost portion, that is, the
cathode of the first auxiliary unit, an active material layer is
preferably coated on only one side facing the radical unit (one side
facing downward in FIG. 12) among both sides of the current collector.
When the one side of the current collector is coated with the active
material layer as described above, the active material layer is not
positioned at the outermost portion of the cell stack part. Thus, waste
of the active material layer may be prevented. For reference, since the
cathode emits, for example, lithium ions, when the cathode is positioned
at the outermost portion, the capacity of a battery may be improved.

[0091] Next, a second auxiliary unit will be described below. The second
auxiliary unit performs the same function as the first auxiliary unit,
which will be described below in more detail. In the present disclosure,
an electrode is positioned at one end of the radical unit, and a
separator is positioned at the other end of the radical unit. When the
radical units are stacked in sequence, the separator may be positioned at
the uppermost portion or at the lowermost portion of the cell stack part
(see reference numeral 117 in FIG. 14, and this separator may be referred
to as a terminal separator 117). The second auxiliary unit is
additionally stacked on the terminal separator.

[0092] In more detail, when the electrode 113 contacting the terminal
separator 117 is a cathode in the radical unit, the second auxiliary unit
140a may be formed by stacking from the terminal separator 117, an anode
111, a separator 112, and a cathode 113 in sequence, as illustrated in
FIG. 14. On the other hand, when the electrode 113 contacting the
terminal separator 117 is an anode in the radical unit, the second
auxiliary unit 140b may be formed as the cathode 111, as illustrated in
FIG. 15.

[0093] In the cell stack parts 100f and 100g, a cathode may be positioned
at the outermost portion of a terminal separator through the second
auxiliary units 140a and 140b, as illustrated in FIGS. 14 and 15. In this
case, in the cathode positioned at the outermost portion, that is, the
cathode of the second auxiliary unit, an active material layer is
preferably coated on only one side facing the radical unit (one side
facing upward in FIG. 14) among both sides of the current collector, as
similar to the cathode of the first auxiliary unit.

[0094] The first auxiliary unit and the second auxiliary unit may have
different structures from those described above. First, the first
auxiliary unit will be described below. When the terminal electrode 116
is a cathode as illustrated in FIG. 16, the first auxiliary unit 130c may
be formed by stacking from the terminal electrode 116, a separator 114,
and an anode 113 in sequence. On the other hand, when the terminal
electrode 116 is an anode as illustrated in FIG. 17, the first auxiliary
unit 130d may be formed by stacking from the terminal electrode 116, a
separator 114, a cathode 113, a separator 112, and an anode 111 in
sequence.

[0095] In the cell stack parts 100h and 100i, an anode may be positioned
at the outermost portion of the terminal electrode through the first
auxiliary units 130c and 130d, as illustrated in FIGS. 16 and 17.

[0096] Next, the second auxiliary unit will be described below. As
illustrated in FIG. 18, when the electrode 113 contacting the terminal
separator 117 is a cathode in the radical unit, the second auxiliary unit
140c may be formed as an anode 111. As illustrated in FIG. 19, when the
electrode 113 contacting the terminal separator 117 is an anode in the
radical unit, the second auxiliary unit 140d may be formed by stacking
from the terminal separator 117, the cathode 111, the separator 112, and
the anode 113 in sequence. In the cell stack parts 100j and 100k, an
anode may be positioned at the outermost portion of the terminal
separator through the second auxiliary units 140c and 140d, as
illustrated in FIGS. 18 and 19.

[0097] For reference, an anode may make a reaction with an aluminum layer
of a battery case (for example, a pouch-type case) due to potential
difference. Thus, the anode is preferably insulated from the battery case
by means of a separator. For this, the first and second auxiliary units
in FIGS. 16 to 19 may further include a separator at the outer portion of
the anode. For example, the first auxiliary unit 130e in FIG. 20 may
further include a separator 112 at the outermost portion thereof when
compared to the first auxiliary unit 130c in FIG. 16. For reference, when
the auxiliary unit includes the separator, the alignment of the auxiliary
units in the radical unit may be easily performed.

[0098] A cell stack part 100m may be formed as illustrated in FIG. 21. A
radical unit 110b may be formed by stacking from the lower portion to the
upper portion, a first electrode 111, a first separator 112, a second
electrode 113, and a second separator 114 in sequence. In this case, the
first electrode 111 may be a cathode, and the second electrode 113 may be
an anode.

[0099] A first auxiliary unit 130f may be formed by stacking from the
terminal electrode 116, the separator 114, the anode 113, the separator
112 and the cathode 111 in sequence. In this case, in the cathode 111 of
the first auxiliary unit 130f, only one side of a current collector
facing the radical unit 110b among both sides of the current collector
may be coated with an active material layer.

[0100] Also, a second auxiliary unit 140e may be formed by stacking from
the terminal separator 117, the cathode 111 (the first cathode), the
separator 112, the anode 113, the separator 114, and the cathode 118 (the
second cathode) in sequence. In this case, in the cathode 118 (the second
cathode) of the second auxiliary unit 140e positioned at the outermost
portion, only one side of a current collector facing the radical unit
110b among both sides of the current collector may be coated with an
active material layer.

[0101] Finally, a cell stack part 100n may be formed as illustrated in
FIG. 22. A radical unit 110e may be formed by stacking from the upper
portion to the lower portion, a first electrode 111, a first separator
112, a second electrode 113, and a second separator 114 in sequence. In
this case, the first electrode 111 may be an anode, and the second
electrode 113 may be a cathode. Also, a second auxiliary unit 140f may be
formed by stacking from the terminal separator 117, the anode 111, the
separator 112, the cathode 113, the separator 114, and the anode 119 in
sequence.

[0102] Until now, the structure of the radical unit, the structure of the
auxiliary unit that may be stacked on the radical unit, and the structure
of the cell stack part having the plurality of stacked radical units have
been explained. Hereinafter, the manufacturing of the cell stack part
(electrode assembly) by forming a sealing part A at the radical unit
itself or by forming a sealing part A at the cell stack part at the same
time will be explained referring to the first radical unit illustrated in
FIG. 2 for convenience.

[0103] The electrode assembly may correspond to the cell stack part itself
or the cell stack part wrapped in a tape for fixing. Thus, the electrode
assembly according to the present disclosure is provided with a cell
stack part having a repeatedly stacked structure of one kind of the
radical units including the same number of alternately stacked electrodes
and separators, or having a stacked structure of two or more kinds of the
radical units including the same number of alternately stacked electrodes
and separators in a predetermined order.

[0104] FIG. 23 is a cross-sectional view illustrating a stacked state of a
separator on a first structure of the radical unit in FIG. 2, and FIG. 24
is a cross-sectional view illustrating a stacked state of a separator on
an uppermost electrode after stacking a first structure of the radical
unit in FIG. 2 twice.

[0105] As shown in FIGS. 23 and 24, a separator S is additionally stacked
on the uppermost electrode of the cell stack part, and the top surface of
the uppermost electrode and the bottom surface of the lowermost electrode
are covered with separators. When the cell stack parts shown in FIGS. 23
and 24 are turned up and down, the separators S may be additionally
stacked on the lowermost electrodes of the cell stack parts.

[0106] The edge portions of adjacent separators in FIGS. 23 and 24 are
placed to meet each other, and heat and pressure are applied to attach
the edge parts of the separators, thereby forming sealing parts A
illustrated in FIGS. 25 and 26.

[0107] Meanwhile, the sealing part A may be formed by attaching the edge
parts of the separators included in one radical unit during manufacturing
the electrode assembly. Alternatively, the sealing part A may be formed
by stacking the radical units (of course, the auxiliary unit may be
stacked together) to form the cell stack part and then, attaching the
edge parts of all of the separators included in the cell stack parts
together.

[0108] Hereinafter, an embodiment of the manufacturing method of the
electrode assembly according to the present invention will be described
in more detail.

[0109] First, a step of manufacturing one kind of radical units having an
alternately stacked structure of the same number of electrodes and
separators or two, or more kinds of radical units having an alternately
stacked structure of the same number of electrodes and separators is
conducted (S10).

[0110] Then, a step of placing the edge parts of the separators included
in one radical unit to meet each other, and forming a sealing part A by
applying heat and pressure is conducted (S20).

[0111] After that, a step of manufacturing a cell stack part is conducted
by repeatedly stacking one kind of the radical units after performing
Step S10 and Step S20, or by stacking two or more kinds of the radical
units after performing Step S10 and Step S20 in order (S22).

[0112] As described above, after forming the sealing part A of the edge
parts of the separators in each of the radical units by performing Steps
S10, S20 and S22 in sequence, a cell stack part (an electrode assembly)
having a stacked structure of the radical units may be manufactured.

[0113] In another embodiment of the manufacturing method of the electrode
assembly according to the present disclosure, Step S10 is performed first
as in the above embodiment, and a step of manufacturing a cell stack part
by repeatedly stacking one kind of the radical units or by stacking two
or more kinds of the radical units in order is performed (S14). Then, the
edge parts of separators included in the cell stack part are placed to
meet each other, and heat and pressure are applied to form a sealing part
A (S30).

[0114] Through conducting Steps S10, S14 and S30 in sequence, a cell stack
part is manufactured first by stacking the radical units without forming
the sealing part A from the edge parts of the separators provided in the
radical units, and then, the sealing part A is formed by using the edge
parts of all the separators included in the cell stack part at the same
time.

[0115] When the cell stack part shown in FIG. 4 is assumed to be
manufactured by stacking the first radical units, and an additional
separator S is stacked on the uppermost electrode of the first radical
unit positioned at the uppermost portion of the cell stack part in FIG.
4, a cell stack part including the separators at both of the uppermost
and the lowermost parts may be manufactured.

[0116] Meanwhile, the heat and the pressure applied to the edge parts of
adjacent separators to form the sealing part A in Step S20 and Step S30,
are preferably and respectively 50° C. to 100° C. and 10
gf/cm2 to 20 gf/cm2. In addition, the formation of a
satisfactory sealing part A may be performed by only applying the heat
and the pressure to the edge parts of the adjacent separators for 3 to 5
seconds in Step S20 or Step S30.

[0117] Accordingly, the time necessary for the manufacture of electrode
assembly may not significantly increase due to the forming steps (S20 and
S30) of the sealing part A.

[0118] A pressure of about 100 Kgf/cm2 is necessary to attach the
cathode and the anode, on the contrary, the above described pressure of
10 gf/cm2 to 20 gf/cm2 applied to the edge parts of the
separators for the formation of the sealing part A is sufficient. Thus,
the sealing part A may be formed by applying significantly less pressure
than that applied to attach the cathode and the anode to the separator.

[0119] Hereinafter, experiments performed to verify the effects of the
electrode assembly of the present disclosure will be described.

Comparative Example

[0120] In an electrode assembly in which the edge parts of separators were
not overlapped, 20 to 24% of shrinkage ratio was found after heating at
150° C. for 30 minutes.

Experimental Example 1

[0121] In an electrode assembly in which the edge parts of separators were
overlapped but not attached, and a sealing part A was not formed, 16 to
18% of shrinkage ratio was found after heating at 150° C. for 30
minutes.

Experimental Example 2

[0122] In an electrode assembly in which the edge parts of separators were
attached, and a sealing part A was formed, 9 to 12% of shrinkage ratio
was found after heating at 150° C. for 30 minutes.

[0123] When comparing the shrinkage ratio of Experimental Example 1 with
that of Comparative Example, the shrinkage ratio of the separator was
found to decrease when the edge parts of the separator were overlapped
when compared to that of the separator when the edge parts of the
separators were not overlapped and separately stacked between the
cathodes and the anodes.

[0124] In addition, when comparing the shrinkage ratio of Experimental
Example 2 with that of Experimental Example 1, the shrinkage ratio of the
separator was found to decrease when the edge parts of the separators
were overlapped and attached to form a sealing state when compared to
that of the separators simply and doubly overlapped at the edge parts of
the separators.

[0125] In the electrode assembly according to the present disclosure, the
decreasing effect of the shrinkage ratio due to the overlapping and the
decreasing effect of the shrinkage ratio due to the attachment of the
separators are combined, and the shrinkage ratio of the separators may be
markedly decreased.

[0126] Accordingly, the possibility of generating short between the
cathode and the anode is very low, and the stability of the electrode
assembly is improved in the present disclosure when compared to a common
technology. In addition, an electrode assembly having improved stability
when considering the common electrode assembly may be manufactured even
though a separator having the same size or somewhat smaller size than the
common technology is used.

[0127] Since the area of the separator necessary for the manufacture of an
electrode assembly having the stability similar to that of the common
technology is smaller than the common technology, the volume of a
secondary battery may decrease.

[0128] In addition, since a separator having a smaller area when
considering the common technology is used, the production cost of an
electrode assembly may decrease.

[0129] While the present invention has been shown and described in
connection with the exemplary embodiments, it will be apparent to those
skilled in the art that modifications and variations can be made without
departing from the spirit and scope of the invention as defined by the
appended claims.